1. Field of the Invention
The present invention relates to an optical axis adjustment device. More specifically, the present invention relates to an optical axis adjustment device that can properly determine a distance between the viewer and a target object.
2. Description of the Prior Art
A laser ruler is a laser based distance-measuring device, which is an important tool for measuring a distance in the modern industry. The laser ruler operates by measuring a time period in which a laser pulse or laser pulse sequence travels from a laser transmitter to a target object and travels back from the target object to a laser receiver. The distance between the laser ruler and the target object can be obtained by multiplying half of the time period by light speed. An example of the conventional laser based distance-measuring equipment, such as the laser ruler, is disclosed in Taiwan Patent No. 417783, comprising a laser transmitter, a laser receiver perpendicular to the laser transmitter, a prism (or a reflective lens) disposed in front of the laser transmitter on the progressing path of a laser beam transmitted from the transmitter, for reflecting the transmitted laser beam toward the target object. Theoretically, laser beam reflected from the target object is parallel to the optical axis and is received by the laser receiver. By calculating the time period of traveling, a precise distance value is obtained. However, in fact, because the distance between the target object and the laser distance-measuring equipment is finite, a certain included angle between the optical axis of the transmitted laser beam toward the target object and that of reflected laser beam from the target object exists, resulting in an error in distance calculation. In order to avoid the error, position or angle calibration for the prism or the laser transmitter to make the reflected laser beam exactly aiming the center of the laser receiver is required. This indicates that the optical axis of transmitted laser beam reflected by the prism and that of laser beam reflected from the target object exactly intercrosses at the point of target object. Meanwhile, keeping the axis of the transmitted laser beam and that of received laser beam in the same spatial plane is essential.
A conventional adjustment mechanism for use in laser distance-measuring equipment, disclosed in Taiwan Patent No. 417783, comprises a first connecting portion disposed on the main body of the laser distance-measuring equipment, a second connecting portion disposed on the laser transmitter, a pair of bolts disposed between the first connecting portion and the second connecting portion. The second connecting portion is movably engaged with the first connecting portion by using a bolt. In doing so, depending on actual measurement condition and environment, a vertical and horizontal position of the second connecting portion relative to the first connecting position is adjusted by using the bolt, achieving the goal of adjusting the laser distance-measuring equipment. However, it is necessary to install a bolt at the both sides of the laser distance-measuring equipment (as shown in FIG. 5 in Taiwan Patent No. 417783), leading to a larger size of the laser distance-measuring equipment, especially in width, and inconvenience for carrying. Furthermore, the adjustment mechanism can simply calibrate one direction, not meeting the reality requirement for precision measurement in various condition and environment. Therefore, it is necessary to provide an adjustment mechanism for calibrating 3-dimension direction of the laser distance-measuring equipment and capable of reducing the size of the laser distance-measuring equipment, to meet a tendency of size-miniaturizing and high precision for such equipment.